SAR Interferometry (InSAR): principles

Slides:



Advertisements
Similar presentations
Microwave remote sensing applications and it’s use in Vietnam
Advertisements

Detection of weak optical signals D.R. Selviah, R.C. Coutinho, H.A. French and H.D. Griffiths Department of Electronic and Electrical Engineering, University.
Shapelets Correlated with Surface Normals Produce Surfaces Peter Kovesi School of Computer Science & Software Engineering The University of Western Australia.
USEReST - Naples 2008 Terrain Deformation Monitoring with PSInSAR TM Marco Bianchi Sensing the planet Marco Basilico
On Estimation of Soil Moisture & Snow Properties with SAR Jiancheng Shi Institute for Computational Earth System Science University of California, Santa.
Batch processing, stacking and time series analysis
Chapter Fifteen: Radio-Wave Propagation
Lecture 12 Content LIDAR 4/15/2017 GEM 3366.
Resolution Resolving power Measuring of the ability of a sensor to distinguish between signals that are spatially near or spectrally similar.
Motion of Glaciers, Sea Ice, and Ice Shelves in Canisteo Peninsula, West Antarctica Observed by 4-Pass Differential Interferometric SAR Technique Hyangsun.
Radar Remote Sensing RADAR => RA dio D etection A nd R anging.
Millimeter Wave Sensor: An Overview
Airborne Laser Scanning: Remote Sensing with LiDAR.
SURVEYING II UNIT IV PRESENTATION II.
Remote sensing in meteorology
7 th CNES/DLR Workshop LISTIC / TSI / GIPSA-lab / MAP-PAGE1 High Resolution SAR Interferometry: estimation of local frequencies in the context of Alpine.
Optics in Astronomy - Interferometry - Oskar von der Lühe Kiepenheuer-Institut für Sonnenphysik Freiburg, Germany.
Remote Sensing: John Wilkin Active microwave systems (4) Coastal HF Radar IMCS Building Room 214C ext 251 Dunes of sand.
Remote Sensing: John Wilkin Active microwave systems Coastal HF Radar IMCS Building Room 214C ph: Dunes of sand and seaweed,
Time-series InSAR with DESDynI: Lessons from ALOS PALSAR Piyush Agram a, Mark Simons a and Howard Zebker b a Seismological Laboratory, California Institute.
What is RADAR? What is RADAR? Active detecting and ranging sensor operating in the microwave portion of the EM spectrum Active detecting and ranging sensor.
Introduction This SAR Land Applications Tutorial has three main components: Background and theory - an overview of the principles behind SAR remote sensing,
Space remote sensing for urban damage detection mapping and mitigation Salvatore Stramondo 1, Nazzareno Pierdicca 2, Marco Chini 3, Christian Bignami 1.
Remote Sensing and Active Tectonics Barry Parsons and Richard Walker Michaelmas Term 2011 Lecture 4.
IGARSS 2011 – July, Vancouver, Canada Investigating the seismic cycle in Italy by multitemporal analysis of ALOS, COSMO-SkyMed and ERS/Envisat DInSAR.
Random Media in Radio Astronomy Atmospherepath length ~ 6 Km Ionospherepath length ~100 Km Interstellar Plasma path length ~ pc (3 x Km)
INTERFEROMETRIC ERROR SOURCES
WMO/ITU Seminar Use of Radio Spectrum for Meteorology Earth Exploration-Satellite Service (EESS)- Active Spaceborne Remote Sensing and Operations Bryan.
Dr A VENGADARAJAN, Sc ‘F’, LRDE
DOCUMENT OVERVIEW Title: Fully Polarimetric Airborne SAR and ERS SAR Observations of Snow: Implications For Selection of ENVISAT ASAR Modes Journal: International.
GISMO Simulation Study Objective Key instrument and geometry parameters Surface and base DEMs Ice mass reflection and refraction modeling Algorithms used.
Long Time Span Interferograms and Effects of Snow Cover on Interferometric Phase at L-Band Khalid A. Soofi (ConocoPhillips), David Sandwell (UCSD, SCRIPPS)
Certified Wireless Network Administrator (CWNA) PW0-105 Chapter 2 Radio Frequency Fundamentals.
SWOT Near Nadir Ka-band SAR Interferometry: SWOT Airborne Experiment Xiaoqing Wu, JPL, California Institute of Technology, USA Scott Hensley, JPL, California.
1 SPACE BORNE RADAR INTERFEROMETRIC MAPPING OF PRECURSORY DEFORMATIONS OF A DYKE COLLAPSE, DEAD SEA, JORDAN Closson, Abou Karaki, al-Fugha
1-1 SWOT IGARSS July 27, 2011 INTERFEROMETRIC PROCESSING OF FRESH WATER BODIES FOR SWOT Ernesto Rodríguez, JPL/CalTech Delwyn Moller, Remote Sensing Solution.
Chapter 8 Remote Sensing & GIS Integration. Basics EM spectrum: fig p. 268 reflected emitted detection film sensor atmospheric attenuation.
Napoli, – USEReST 2008 VOLCANO MONITORING VIA FRACTAL MODELING OF LAVA FLOWS Gerardo DI MARTINO Antonio IODICE Daniele RICCIO Giuseppe RUELLO.
Interferometric Synthetic-Aperture Radar (InSAR) Basics
I hope its ok to do these InSAR exercises as the lab
Persistent Scatterers in InSAR
Chapters 16, 17 Waves.
How does InSAR work? Gareth Funning University of California, Riverside.
Atmospheric phase correction at the Plateau de Bure interferometer IRAM interferometry school 2006 Aris Karastergiou.
Centre Spatial de Liège Institut Montefiore
InSAR Processing and Applications
InSAR Application for mapping Ice Sheets Akhilesh Mishra Dec 04, 2015.
Introduction to Interferometric Synthetic Aperture Radar - InSAR
Time Dependent Mining- Induced Subsidence Measured by DInSAR Jessica M. Wempen 7/31/2014 Michael K. McCarter 1.
Active Remote Sensing for Elevation Mapping
RADAR.  Go through intro part of LeToan.pdfhttp://earth.esa.int/landtraining07/D1LA1- LeToan.pdf.
SCM x330 Ocean Discovery through Technology Area F GE.
Fault Plane Solution Focal Mechanism.
ARENA08 Roma June 2008 Francesco Simeone (Francesco Simeone INFN Roma) Beam-forming and matched filter techniques.
2003 Tyrrhenian International Workshop on Remote Sensing INGV Digital Elevation Model of the Alban Hills (Central Italy) from ERS1-ERS2 SAR data Andrea.
Layover Layover occurs when the incidence angle (  ) is smaller than the foreslope (  + ) i.e.,  <  +. i.e.,  <  +. This distortion cannot be corrected!
GEOGG141 / GEOG3051 Principles & Practice of Remote Sensing (PPRS) RADAR II: Interferometry Dr. Mathias (Mat) Disney UCL Geography Office: 113, Pearson.
Class tutorial Measuring Earthquake and volcano activity from space Shimon Wdowinski University of Miami.
HSAF Soil Moisture Training
Shadowing.
Active Microwave Remote Sensing
(2) Norut, Tromsø, Norway Improved measurement of sea surface velocity from synthetic aperture radar Morten Wergeland Hansen.
Active Remote Sensing for Elevation Mapping
GEOGRAPHIC INFORMATION SYSTEMS & RS INTERVIEW QUESTIONS ANSWERS
2nd URSI-Regional Conference on Radio Science (URSI-RCRS-2015)
Closson, Abou Karaki, al-Fugha
Dr. Mathias (Mat) Disney UCL Geography Office: 113, Pearson Building
LightGage™ Frequency Scanning Technology
이훈열, 조성준, 성낙훈 강원대학교 지구물리학과 한국지질자원연구원 지반안전연구부
Remote sensing in meteorology
Presentation transcript:

SAR Interferometry (InSAR): principles INGV SAR Interferometry (InSAR): principles Salvatore Stramondo Antonio Montuori Istituto Nazionale di Geofisica e Vulcanologia salvatore.montuori@ingv.it antonio.montuori@ingv.it Corso presso Univ. della Calabria 10/04/2017

Summary Interferometry SAR Interferometry (InSAR) technique: theory. Differential InSAR (DInSAR): general aspects. Multi-Temporal DInSAR techniques: SBAS & PSI Corso presso Univ. della Calabria 10/04/2017

Interferometry Interferometry refers to a family of techniques in which electromagnetic waves are coherently combined in order to extract information about the waves. An instrument used to interfere waves is called an interferometer. Interferometry is an important investigative technique in the fields of astronomy, fiber optics, engineering metrology, optical metrology, oceanography, seismology, quantum mechanics, nuclear and particle physics, plasma physics, remote sensing and biomolecular interactions. Corso presso Univ. della Calabria 10/04/2017

SAR Interferometry (InSAR) InSAR technique is a powerful tool to retrieve the position and/or the displacement of surface point scatterers through the pixel-to-pixel phase difference processing of couple SAR images acquired over the same scene viewed from comparable well-known acquisition geometries. We call interferogram the image of the pixel to pixel phase differences. An interferogram is a complex image with (a) magnitude given by the product of the SAR amplitudes and (b) phase (the InSAR phase) given by the path length difference, as well as variations of the scattering properties and the medium conditions. Corso presso Univ. della Calabria 10/04/2017

SAR Interferometry (InSAR) The recorded phase is composed by two terms: the propagation phase, relevant to the sensor-to-target distance the backscattered phase, due to the surface backscattering The backscattered phase is obtained as the sum of the phase contribution of each scatterer within the resolution cell on the plane perpendicular to the satellite LOS Corso presso Univ. della Calabria 10/04/2017

SAR Interferometry (InSAR) baseline Bn Bp Two radar antennas mounted on board of two satellite-based SARs (1 and 2) observe a target with a slight separation in space (the interferometric spatial baseline). Bp is the parallel spatial baseline Bn is the parallel spatial baseline If the two images are acquired simultaneously  single-pass interferometry If the two images are acquired at different times  repeat-pass interferometry Corso presso Univ. della Calabria 10/04/2017

SAR Interferometry (InSAR) Along-track InSAR mode: The two SAR antennas are along-track aligned and acquire the scattered electromagnetic field at slightly different times. This mode is exploited to estimate the sea surface spectrum. This mode is obviously operated in a single-pass. Across-track InSAR mode: The two SAR antennas are aligned across-track. This mode can be operated both in single-pass and multi-pass configurations. This mode is used to estimate the Digital Elevation Model (DEM). Corso presso Univ. della Calabria 10/04/2017

SAR Interferometry (InSAR) SAR vs InSAR

SAR Interferometry (InSAR) Whenever the surface backscattering is unchanged (high coherence degree), the signal (S) received by the SAR from a target at distance R has an amplitude (A) related to the scattering strength of the target and a phase () related to the two-way traveling wave path between the radar and the target:

SAR Interferometry (InSAR) Be S1 and S2 the received signals at two satellite positions: The interferogram is the map of the pixel-to-pixel phase differences between S1 and S2: baseline Bn Bp Corso presso Univ. della Calabria 10/04/2017

SAR Interferometry (InSAR) The two complex SAR images must be coregistered by interpolating one image (the slave image) to generate imagery at the same pixel locations as the second (the master image). After registration, the two complex SAR images are multiplied, and the interferometric phase is obtained. Corso presso Univ. della Calabria 10/04/2017

SAR Interferometry (InSAR) The interferometric phase contains some distinct contributions: flat Earth topographic phase deformation phase atmospheric phase noise (error phase) Corso presso Univ. della Calabria 10/04/2017

SAR Interferometry (InSAR) Flat Earth Raw interferogram includes a quasi-linear phase trend caused by tilt of terrain surface relative to the baseline Flattening removes interferometric phase component using a sphere with radius of curvature derived from the ellipsoid. Corso presso Univ. della Calabria 10/04/2017

SAR Interferometry (InSAR) Flat Earth Unflattened interferogram Flattened interferogram Corso presso Univ. della Calabria 10/04/2017

SAR Interferometry (InSAR) Flat Earth Unflattened interferogram Flattened interferogram

SAR Interferometry (InSAR) Topographic phase The topographic phase contains the information relative to the relief. The spacing between the fringes depends on the perpendicular baseline: the longer the perpendicular baseline, the narrower the fringes B=174 m B=40 m Corso presso Univ. della Calabria 10/04/2017

SAR Interferometry (InSAR) Topographic phase Baseline doubling Corso presso Univ. della Calabria 10/04/2017

SAR Interferometry (InSAR) Topographic phase The ambiguity height is the elevation difference corresponding to a full phase cycle (2): ERS satellites: Corso presso Univ. della Calabria 10/04/2017

SAR Interferometry (InSAR) Phase ambiguity The interferometric phase is generally modulus 2p. A phase unwrapping method can be then applied to calculate the exact phase value in order to extract correct information about the scene (the elevation). Corso presso Univ. della Calabria 10/04/2017

SAR Interferometry (InSAR) Phase ambiguity The interferometric phase component is known save for 2Np: Phase unwrapping algorithms can be applied to retrieve from the “wrapped phase” : Corso presso Univ. della Calabria 10/04/2017

SAR Interferometry (InSAR) Phase ambiguity Branch-cut region growing algorithm: it is based on the identification of branches linking the areas with phase continuities. It is typically applied to the filtered interferograms. Critical areas, such as areas of very low coherence or residues, are identified and avoided in the phase unwrapping. Minimum Cost Flow (MCF) techniques and Triangular Irregular Network (TIN): global optimization technique to the phase unwrapping problem (for example at locations of very low coherence) which provides high density of unwrapped points together with an efficient and robust unwrapping Corso presso Univ. della Calabria 10/04/2017

SAR Interferometry (InSAR) Phase ambiguity Corso presso Univ. della Calabria 10/04/2017

SAR Interferometry (InSAR) From SAR raw data to Interferogram Corso presso Univ. della Calabria 10/04/2017

SAR Interferometry (InSAR) Atmospheric phase Corso presso Univ. della Calabria 10/04/2017

SAR Interferometry (InSAR) Atmospheric phase The phase due to atmospheric artifacts does not depend on the baseline and its sensitivity to the atmosphere is related to the wavelength (Longer wavelengths are less sensitive to atmospheric distortions). A propagation delay (Dl) of 2cm would result in an additional phase of an almost full fringe at C-band but only of 1/6th of a fringe at L-band. In case of stronger delays, the spatial phase variations might be so large that at higher frequencies phase unwrapping could fail because of more cycles being wrapped. Corso presso Univ. della Calabria 10/04/2017

SAR Interferometry (InSAR) Tropospheric effects Interferogram B perp. =5 m B temp.=55gg SAR ERS intensity image of the Apennine Corso presso Univ. della Calabria 10/04/2017

SAR Interferometry (InSAR) Complex coherence The degree of correlation between two SAR images is measured by the coherence parameter. The amplitude is the degree of coherence, the phase is the interferometric phase. Coherence is a measure of the phase noise or fringe visibility Corso presso Univ. della Calabria 10/04/2017

SAR Interferometry (InSAR) Complex coherence Interferometric phase Coherence Corso presso Univ. della Calabria 10/04/2017

SAR Interferometry (InSAR) Complex coherence The spatial coherence can be filtered out. A part remains if we have a volume (forest, snow, city). This is called volume decorrelation and increases with the spatial baseline. The temporal coherence can NOT be filtered out, it is a property of the image. This is also referred to as temporal decorrelation term and depends on the stability of the objects between the two acquisitions. Corso presso Univ. della Calabria 10/04/2017

SAR Interferometry (InSAR) Complex coherence Geometric decorrelation: it relies on the sight angle differences of the two SAR scenes part of the interferogram. The critical value of the baseline at which complete decorrelation occurs is given by: For ERS and ENVISAT the critical baseline is about 1100 m (R=850 km, =23º, Lc=25m, =5.6 cm). For JERS-1 and PALSAR the critical baseline is about 4 km (R=730 km, =35º, Lc=25m, =23 cm). Corso presso Univ. della Calabria 10/04/2017

SAR Interferometry (InSAR) Complex coherence Corso presso Univ. della Calabria 10/04/2017

SAR Interferometry (InSAR) Complex coherence The two SAR antennas see the scene under slightly different angles, hence they record different parts of the image spectrum shifted by an amount f. Spectrum1 Spectrum2 If the spectrum shif is equal to the critical one (see the formula above), they automatically loose part of the correlation they have (spatial decorrelation). Spectral shift filtering removes the effect of spatial decorrelation for level surfaces. There is a proportional loss of range resolution. Corso presso Univ. della Calabria 10/04/2017

SAR Interferometry (InSAR) Complex coherence In the repeat-pass configuration the scatterers may move (e.g. water surfaces and tree canopies) or their dielectric properties may change (e.g. snow, wet soils) between observations. The two SAR images are only partially correlated because of the temporal interval between the acquisitions. In general it is likely that the longer the time interval between acquisitions, the stronger the temporal decorrelation. Taking into account that typically temporally unstable scatterers have dimensions of the order of a few centimeters or less (e.g. leaves, grass, snow grains etc.), temporal decorrelation is more pronounced at shorter wavelengths (e.g. at X- and C-band). Corso presso Univ. della Calabria 10/04/2017

SAR Interferometry (InSAR) Spatial decorrelation effects 06/02/1997-22/05/1997 Baseline ort. = 330 m 22/05/1997-18/12/1997 Baseline ort. = 40 m Corso presso Univ. della Calabria 10/04/2017

SAR Interferometry (InSAR) Temporal decorrelation effects 07/05/1996-08/05/1996 Baseline temp. = 1 day 02/06/1999-06/02/2002 Baseline temp. = 980 days Baseline ort. = 3 m Corso presso Univ. della Calabria 10/04/2017

Differential SAR Interferometry (DInSAR) Differential SAR Interferometry (DInSAR) is an InSAR technique addressed to measure the Earth surface displacements with centimetric accuracy. DInSAR is used in seismology, for instance, when an earthquake takes place. Two SAR images, one pre-seismic and one post-seismic, are acquired. The interferometric phase is computed. Using a DEM, the topographic phase is canceled. The residual phase contains also the eventual surface deformation effect (differential interferogram). Each differential fringe corresponds to a full phase cycle (2p) and represents a sensor-to-target distance change (LOS change) of l/2. For C-Band sensors it is about 2.8 cm. Corso presso Univ. della Calabria 10/04/2017

Differential SAR Interferometry (DInSAR) Be S1 and S2 two SAR satellites. The interferometric phase is: The residual phase contains, besides atmosphere and Noise phase component, the displacement projected onto the LOS. Corso presso Univ. della Calabria 10/04/2017

Differential SAR Interferometry (DInSAR) Objective of DInSAR: Separation of topo from total phase to determine displ 2-pass: Simulate topo based on existing DEM. Phase unwrapping not required for the simulated interferogram. High accuracy of DEM required. 3- and 4-pass: Derive topo from independent interferogram, no existing DEM is required but phase unwrapping required. The combination of complex interferograms may be of interest to do a kind of differential interferometry without phase unwrapping and geocoding requirement to improve the sensitivity to topography. Corso presso Univ. della Calabria 10/04/2017

Differential SAR Interferometry (DInSAR) Consider a standard deviation on phase and displacement: For ERS: Corso presso Univ. della Calabria 10/04/2017

Differential SAR Interferometry (DInSAR) Multi-Temporal DInSAR In conclusion... InSAR Configurations Along-Track InSAR (∆t = ms to s) Across-Track InSAR (∆θ) DInSAR (∆t = giorni - anni) Multi-Temporal DInSAR Field of Application Oceanic current & Target detection Digital Elevation Model (DEM) Surface deformation velocity maps Surface time-series and deformation velocity maps Corso presso Univ. della Calabria 10/04/2017

Principi di base – Interferometria SAR Evolution of Satellite-based DInSAR: Multi-temporal DInSAR Time series and deformation velocity maps of observed surface. Main Multi-Temporal DInSAR Techniques “Small BAseline Subset (SBAS)” Super-Master reference SAR image Different subsets of SAR images “Small” spatial and temporal baselines “Linking” among SAR subsets Reference Scatter points with high interferometric coherence values Poor spatial resolution

Principi di base – Interferometria SAR Evolution of Satellite-based DInSAR: Multi-temporal DInSAR Time series and deformation velocity maps of observed surface. Main Multi-Temporal DInSAR Techniques “Persistent Scatterers Interferometry (PSI)” Unique “Reference master” SAR “Large” spatial and temporal baselines Scatter points smaller than resolution cell dimensions Persistent scatter points (stability in terms of SAR amplitude) High spatial resolution